Method for assembling electric motors

ABSTRACT

The specification describes a method for assembling electric motors comprising a casing and opposite head members co-axial therewith, including the step of permanently securing said head members to said casing by inwardly clinching the end portions of said casing to the periphery of the adjacent head member, and electric motors wherein their head members are permanently secured to the motor yoke casing according to the method.

United States Patent Gutris [54] METHOD FOR ASSEMBLING [4 1 Dec. 26,1972

3,439,403 4/1969 Lippmann et a1 ..29/596 x ELECTRIC MOTORS 3,508,3274/1970 Diederichs et al ..29/$96 72 I t Gio o Gutris 49, Viale Certosa,1 men or Mug Italy Primary Examiner-John F. Campbell AssistantExaminer-Carl E. Hall [22] Flled: 1970 Attorney-Wenderoth, Lind & Ponack21 Appl. No.: 86,531

v. 3 L 11 ABSTRACT [52] us. CI. 29/596, 310/42,310/64, The specificationdescribes a method for assembling 310/89 electric motors comprising acasing and opposite head Int. Cl....H02k 15/ 0, H02k 1 14. H02]: 15/ 16members co-axiai therewith, including the step of per- '[58] Field OfSearch ..29/596; 310/42, 89, 64 manenfly securing said head members tosaid casing by inwardly. clinching the end portions of said casingReferences Cited to the periphery of the adjacent head member, andUNITED STATES PATENTS electric-motors wherein their head members areper- I manently secured to the motor yoke casing according 3,571,921 3/1971 Pleper ..29/596 to the metho 3,289,018 11/1966 Schaefer ..3l0/421,661,135 2/1928 Knight ..29/596 1 Claim, 7 Drawing Figures 3 152-1.? 11 I I v'- 11" :if /I I? :4 4 14 1 f m 1 12 PATENTED [ll-1226 I972 SHEEI2 OF 2 GIORGIO GUTRIS,

INVENTOR ATTORNEY s 1 METHOD FOR ASSEMBLING ELECTRIC MOTORS BACKGROUNDThis invention concerns a method by which the main structural componentsof electric motors can be predisposed for the assembling and fasteningand then assembled and secured with each other. The invention alsoconcerns the motors manufactured and in particular assembled accordingto said method.

The invention is concerned mainly with the production and assembling offractional motors, having a relatively small rated output a few hundredsof watts, at the mostas well as of those motors for which, owing both totheir features and/or to conditions and requirements, of installationand service, no overhauling or reconditioning operations are anticipatedor planned. Otherwise stated, the invention is intended as an advanceand a contribution in the field of the most modern industrial andeconomical trends according to which the motors, mass-produced on thebasis of a highly advanced and qualified technique, should not be liableto failures or to a noticeable wear and tear under the normal operatingconditions, and according to which in the exceptional event of a motorbreakdown,

' the whole motor is replaced instead of having it repaired orreconditioned. As a matter of fact, in-many cases it is botheconomically and technically more convenient to replace a broken-downmotor than to have it repaired, since any repair is a time consumingoperation, results in a more or less long discontinuation of theoperation of machine or other device driven by the same motor andrequires highly skilled specialists.

It has been ascertained that the conventional, heretofore followedtechnique of electric motor production is not up with the above outlinedmodern trends, though meeting all conditions as required to ensure thehighest efficiency of the same motors. in fact, according to currentart, a separate production and machining to close tolerance of motorcasing is required, whereafter the stator pack is centered and fastenedwithin the casing; then, both head plates, carrying the shaft bearings,are secured to the casing and the shaft having the rotor pack isco-axially secured thereto. A very precision fit machining is necessaryfor all components of the frame (casing and head members) and of theparts as screws,

bolts, studs and the related through or dead, threaded or plain holes bywhich the frame components are firmly held together.

All the above machining operations, that are carried out on individualcomponents, shall be performed with very close tolerances, above all toregard to the accurate co-axiality of assembled components. A highlyaccurate machining is required for the annular centering surfaces, sincea constrained mutual engagement would result in irregular deformations,making also more difficult a possibly required subsequent disassembly offrame, while a too loose fit might be of prejudice for said co-axiality.

Even if however the frame components had been most preciselymanufactured, the very assembling hereof would cause a defectivearrangement. As a matter of fact, the use of screw engaged elements forsecuring such components to each other promotes localized tension andtorque stresses in the same components. More particularly, if the motorcasing is made of relatively thin metal sheet as often desirablesuch assteel sheet from 0.5 to 2.0 millimeters thick, for example, thedirection of the pull exerted by spacedly located rods, which connectthe head members and urge same against the casing, is spaced far fromthe cross-sectional area of the casing and induces stresses both in thecasing and in the head members. Additionally, such rods, when passinginside the casing and through the stator pack, are magneticallydisturbing and, when located outside the casing, unfavorably act on thehead members, prejudice the outer appearence of the motor, increases itsoverall dimension, and so on. Still further, a very precise fitting ofsuch rods, parallel to the motor axis, is difiicult and costly.

SUMMARY According to the invention, the assembling of electric motorscan be made, sharply improved and facilitated by having said maincomponents i.e., frame and head members) fastened with one another by afirm permanent deformation of the at least partly superposed adjoiningedge portions thereof.

From another standpoint of view, the invention provides an arrangementby which the various frame components can be co-axially secured to eachother by preliminarily positioning said components in a relativeposition, which can be termed as an assembling position, wherein thedesired co-axially is provided, and then by permanently deforming atleast one of the coabutting components, without modifying said assemblyposition and thereby maintaining said co-axiality.

According to a preferred embodiment of the invention, the stator casingconsists of a substantially thin walled metallic tubular member, and thesecuring of the end portions of said member to the abutting head membersis provided by inwardly clinching said end portions within recessesprovided in the outer peripheral portions of said head members.

Another important advantage of this invention consists in that anyclearance between the thus fastened components is positively eliminatedby such fastening as obtained by said permanent deformation, and therebythe most desirable highly accurate co-axially relationship under whichthe components are kept while performing said permanent deformation isfurther improved. Another advantage consists in that none ofconventional fasteners (screws, bolts, studs and the like) are needed.An added also important advantage consists in the possibility of havingthe casing made of a relatively thin material, without being subjectedto drawbacks common to the conventional thin walled structures.

Consequently, the method according to the invention consists in thatboth the frame and head members are provided with abutting and centeringannular surfaces, as well as with recesses wherein the adjoining portionor portions of abutting components can be tightly engaged by a permanentdeformation thereof, forming such recesses undercutsby which a firmaxial connection of the components is positively ensured.

The electric motors produced and assembled according to the above methodare generally characterized in that their head members are secured tothe casing ends by closed lock joints or by any other equivalent ofengagement of abutting components, obtained by a permanent deformationof at least one of said components.

with any arranged, dimensioned and Different ways and specificprocedures can be made use of for carrying the method of the inventioninto practice as regards both to the provision of components 'andtheirpreliminary assembling in the required positions, as well as to theirpermanent deformation. Though the permanent connection is preferablyobtained by inwardly bordering the casing i.e., toward the motor axis)for engaging its edge portions into annular grooves or notches as formedon the contour of the head plates, close to annular centering surfaces,such permanent deformation or closed lock joint might be obtainedbyhaving .the edges of head plates socketshapedand engaging them ontothe casing ends that are in turn formed with suitable projections, inthe manner of a spigot-'and-socket joint. The closed lock joint may beformed continuously or discontinuously all along the whole contour ofco-abutted componentsnor it may be restricted to uniformly spacedportions or points of the same contour. In accordance with the abovestatements and according to another embodiment of the invention, thecasing consists of a body that may be only generally defined ascylindrical, in that its cross-sectional shape may be other thancircular, for example approximately polygonal, or it may show any othereven more complex shape, and the cylindrical body may be formed shapedlongitudinal fins.

According to such embodiment of the invention, said body is made byextrusion, and preferably of a metal that is particularly suitable forsuch forming procedure, 'such as aluminium.

vThe permanent deformation according to the invention may be performedon said cylindric body and on the edge portions thereof abutting withthe plates, and it has'be'en surprisingly found that the presence ofeven closely spaced fins, to allow for an efficient heat diss ipation,does not materially interfere with the deformation necessary to providethe permanent connection between casing and head members.

I In the following description of not limitative examples of theinvention, as shown in the accompanying drawings, the main features of afew motors made and assembled according to the invention will be setforth.

DRAWINGS assembled components of same motor.

FIG. 4 is a fragmentary cross-sectional view taken in the planeindicated at IV-IV in FIG. 3.

FIG. 5 is a similar cross-sectional view taken through aIDodifiedembodiment of the head plate. I .FIG. 6 is a view similar to that ofFIG. 1, and illustrates another embodiment of the invention.

FIG. 7 is a cross-sectional view of the motor of FIG. 6, taken throughdifferent planes as indicated at VII- VII-VII-- VII in FIG. 6.

PREFERRED EMBODIMENT In the first embodiment of FIG. 1, the motorcomprises a tubular casing 10 with the stator pack 12 fastened inside ofit in known manner, and two head plates 14 (only one thereof beingshown), each carrying a bearing 16 wherein the motor shaft 18 'isrevolvingly supported carrying the rotor pack 20. The structuralcomponents are to be prepared and assembled in such a manner as toensure the most accurate co-axiality of the statorinner surface 22 tothe rotor outer surface 24 in order to minimize and to equalize the airgap between the magnetically linked components.

Aspreviously stated, the casing 10' can advantageously be made of thinwalled steel drawn or welded tubing 26 having a relatively small wallthickness when compared with the conventionally dimensioned casings.Recourse is preferably made, for the production of the body 26, toametal or alloy that can be permanently deformed, and wherein suchdeformation is rigidly maintained, at least in the edge portions 28 ofthe tubular body.

The head plates 14 are fitted with a peripheral rib 30', acting as acentering annulus about which the adjacent end 28 of the casing can befitted, said ribbeing also formed with projections and recesses in theform of a continuous'annular groove, such as indicated at 32 in FIGS. 3and 4, or of notches suitably spaced thereon, such as indicated at 32 inFIG. 5, in order to allow for the formation of a closed lock jointbetween the abutting components, as indicated by the reference numeral34 in FIG. 1 and 54 in FIGS. 6 and 7.

The closed lock joint or permanent deformation shall be performed by aforce sufficient to ensure a firm grip between the thus connectedcomponents. By such a pressure grip, the necessity of r maintainingclose tolerances in the previous machining of components is whollyobviated or at least greatly reduced,-since any possible small clearanceis thus eliminated. Moreover, the pressure grip is uniformly distributedall around the head plate contour thereby preventing any danger of achange in the theoretical co-axiality conditions, that might be causedby a different tightening (or possible loosening) of screws or bolts,which are traditionally spacedly arranged thereabout to ensure saidconnection.

The body 26 of the casing is wholly cylindrical and uniform throughoutwith obvious production advantages. However, when the constructionandservice of the motor require more intense heat dissipation, the headplates or members may be formed with continuous or discontinuous annularprojections, grooves, perforations or the like, resulting in joiningrecesses or undercuts.

In the second embodiment shown in FIGS. 6 and 7, head members similar tothose above described are made use of and their parts are indicated bythe same reference numerals.

However, the cylindrical body 46 is formed with fins 49 and the closedlock joint is formed in the points indicated by 54, that is in theintervals between adjacent fins.

As shown in FIGS. 6 and 7, the interior of the casing is cylindricalwhile the fin ends are circumscribed by a square having curved sides androunded-off comers; however as previously stated,-the cross-sectionalshape might be different and even more complicated.

' As above indicated, the components can be firstly arranged andmaintained, by proper support means, in their relative arrangement andco-axiality and then subjected to clinching-in to provide the desiredpermanent deformation. In the new structure, an even noticeablemisrotational arrangement of the head members, which are not directlyconnected to each other, is irrelevant and can be disregarded, providingthus a substantial saving in labor-time in the preliminary assembling ofparts, provided that the co-axiality and parallelism of said headmembers be ensured. Further, the pressures and the stresses applied tothe parts, to ensure a firm and permanent grip, are noticeably smallerthan those applied by conventional tightening of bolts, nuts andthreaded bars arranged in spaced relationship about the axis of themotor, and the stresses applied in the direction of the axis or parallelthereto are minimized in a structure according to the invention.

The invention has been described and shown as a not restrictive exampleonly and it is to be understood that any equivalent application ofconceptions and technical solutions that may be inferred from what isstated above, will fall within the scope of this invention.

I claim:

1. A method for assembling an electric motor having a casing of asubstantially cylindrical middle component with the motor statorcoaxially and fixedly secured on the interior surface thereof, saidmiddle component having oppositely located open edge end portions, andof oppositely located essentially diskshaped head components havingperipheral portions each of said head component secured in abuttingrelationship with one of said edge end portions, said head componentshaving bearing means for rotatably supporting the motor shaft and rotorcoaxially to said motor stator, comprising individually manufacturingsaid components, providing said substantially cylindrical middlecomponent with integrally formed cooling fins and both said-middlecomponent and said head component edge ends with portions adapted tooverlap one another upon abutment of said components, providinglocalized and spaced recesses in each of said peripheral portions,coaxially abutting and interfitting said components to secureoverlapping of said portions, and fixedly securing said components toeach other by permanently deforming the overlapping edge ends into saidrecesses at selected points of said overlapped portions.

1. A method for assembling an electric motor having a casing of asubstantially cylindrical middle component with the motor statorcoaxially and fixedly secured on the interior surface thereof, saidmiddle component having oppositely located open edge end portions, andof oppositely located essentially diskshaped head components havingperipheral portions each of said head component secured in abuttingrelationship with one of said edge end portions, said head componentshaving bearing means for rotatably supporting the motor shaft and rotorcoaxially to said motor stator, comprising individually manufacturingsaid components, providing said substantially cylindrical middlecomponent with integrally formed coolIng fins and both said middlecomponent and said head component edge ends with portions adapted tooverlap one another upon abutment of said components, providinglocalized and spaced recesses in each of said peripheral portions,coaxially abutting and interfitting said components to secureoverlapping of said portions, and fixedly securing said components toeach other by permanently deforming the overlapping edge ends into saidrecesses at selected points of said overlapped portions.